The present invention regards a process for manufacturing a microintegrated structure protected against contaminating particles, and the thereby obtained microintegrated structure. In particular, the invention may be advantageously applied to a microactuator fixed to an integrated device including the microactuator control circuitry and to a head in a hard-disk read/write unit with double micrometric actuation.
As is known, hard disks are the most widely used data-storage medium; consequently, they are produced in very large volumes, and the maximum data-storage density increases from one year to the next. Hard disks are read and written by actuator devices, the general structure of which is shown in FIGS. 1 and 2 and is described hereinafter.
In particular, FIG. 1 shows a known actuator device 1 of the rotary type comprising a motor 2 (also called xe2x80x9cvoice coil motorxe2x80x9d) fixed to a support body, generally called xe2x80x9cE-blockxe2x80x9d because of its E-like shape in side view (see FIG. 2). The support body 3 has a plurality of arms 4, each of which carries a suspension 5 including a cantilevered lamina. At its end not fixed to the support body 3, each suspension 5 carries a R/W transducer 6 for reading/writing, arranged (in an operative condition) facing a surface of a hard disk 7 so as to perform roll and pitch movements and to follow the surface of the hard disk 7. To this end, the R/W transducer 6 (also referred to as slider) is fixed to a joint, called gimbal or flexure 8, generally formed from the suspension 5 and comprising, for example, a rectangular plate 8a cut on three and a half sides starting from the lamina of the suspension 5, and having a portion 8b connected to the suspension 5 and allowing flexure of the plate 8a under the weight of the slider 6 (see FIG. 3).
In order to increase the data storage density, it has already been proposed to use a double actuation stage, with a first, rougher actuation stage including the motor 2 moving the assembly formed by the support body 3, the suspension 5 and the RIW slider 6 through the hard disk 7 during a coarse search for the track, and a second actuation stage performing a finer control of the position of the slider 6 during tracking. According to a known solution, the second actuation stage comprises a microactuator 10 arranged between the gimbal 8 and the slider 6, as may be seen in FIG. 3, which shows, in exploded view, the end of the suspension 5, the gimbal 8, the slider 6, and the microactuator 10, in this case, of the rotary type. The microactuator 10 is controlled by a signal supplied by control electronics on the basis of a tracking error.
The microactuator 10 is formed by fixed parts and suspended mobile parts. In particular, the latter, when assembling the R/W transducer on the microactuator and forming the connections with the control circuitry, may be displaced and/or may collapse. In addition, stresses may arise in the structure of the microactuator and cause the structure to become fragile.
In order to maintain final assembly processes similar to those used before the introduction of a double actuation stage, and at the same time prevent displacement and collapse, protection systems for the microactuator, in particular encapsulation structures, have been proposed. Since these systems must maintain the necessary mobility of the mobile parts with respect to the fixed parts, they have separation trenches. These trenches may represent privileged channels for entry of contaminating particles.
In particular, contaminating particles are usually of micrometric and submicrometric dimensions and are drawn into the hard-disk driver by the air circulating by virtue of the disk rotation and the rotor movement. The areas that are most subject to contamination are the high-voltage areas, in particular the fixed and mobile arms, which are separated by gaps with average dimensions of 2 xcexcm.
These contaminating particles, as explained, for example, in the article by LiHong Zhang and Ramesh Koka, xe2x80x9cLost data: How a little dirt can do a lot of damagexe2x80x9d, Data Storage, March 1999, can cause irreparable damage to the hard disk or in any case prevent proper operation of the driver.
According to the present invention, a process for manufacturing a microintegrated structure and the thereby obtained microintegrated structure are provided. The microintegrated structure, of semiconductor material, includes a micromotor and an encapsulation structure. The micromotor is externally delimited by a first and a second faces, opposed to one another, and by a side delimitation trench. The encapsulation structure surrounds the micromotor and has a bottom portion facing the second face of the micromotor, and an outer lateral portion facing the side delimitation trench. An outer separation trench extends through the bottom portion of the encapsulation structure, separates a mobile region from the external side portion, and defines, together with the side delimitation trench, a labyrinthic path for contaminating particles. A sealing ring extends on the bottom portion of the encapsulation structure around an inner separation trench separating the mobile region from a fixed central region and closes a gap between the bottom portion and a mobile component connected to the mobile region of the encapsulation structure.